The present invention relates to cooling systems for computers and other electronic devices, and more particularly to low-profile, compact centrifugal air impellers designed to operate at high speeds.
Designers of a wide variety of electronic devices continually strive to provide more utility in smaller packages. Notebook or laptop computers illustrate this trend, in terms of the ongoing efforts to reduce their size and at the same time enlarge their capacity and capability to store and manipulate data. These devices generate heat during use, with increased functionality leading to increased heat generation. Failure to remove excess heat subjects these devices to a variety of risks ranging from reduced efficiency to serious and permanent damage.
Thus, designers of cooling systems for these devices face the dual and competing goals of smaller size and increased capacity for removing heat.
Typically, notebook computers have been designed to incorporate an internal housing or compartment for a dual-inlet, centrifugal type fan. In one conventional design, blades of constant thickness are attached directly to a rotor hub at their leading edges and extend away from the hub in “backwardly-inclined” fashion. This design can be molded with relative ease at low cost, but entails several disadvantages that become more pronounced in a reduced size, higher speed environment. One is the lack of an aerodynamically effective approach to drawing air into the blades. High speeds lead to distortion of the blades, further reducing efficiency and generating unwanted noise.
Efforts to solve these problems have lead to designs featuring structural or guide members along the blades, either on the positive pressure side as in U.S. patent application, Publication No. 2008/0130226 (Yamashita et al.), or on the leeward side as in U.S. patent application, Publication No. 2009/0028710 (Horng et al.). Another known approach involves selectively varying the blade thickness as shown in U.S. Pat. No. 6,579,064 (Hsieh) and U.S. Pat. No. 7,118,345 (Wu et al.).
In yet another approach the blades, particularly including their leading edges, are separated from the primary hub structure. This has been accomplished with an angular plate extending from the hub as shown in U.S. Pat. No. 6,568,907 (Horng et al.), or with a ring supported radially outwardly from the hub, as in U.S. patent application, Publication No. 2008/0226446 (Fujieda) and the aforementioned Wu patent.
Yet another approach is to support the blades individually with posts or other members at their leading edges. Examples of this approach include U.S. Pat. No. 7,063,510 (Takeshita et al.) and U.S. patent application, Publication No. 2007/0274834 (Huang et al.).
Although the forgoing examples and similar approaches have led to improved performance compared to the directly attached linear constant thickness blade design, the above-identified problems persist. Accordingly, the present invention is characterized by several aspects directed to one or more of the following objects:                to provide an impeller with a mounting structure that locates the impeller blades in spaced apart relation to a hub while providing more stable support for the blades;        to provide an impeller including a plurality of struts for supporting a plurality of impeller blades in surrounding, spaced apart relation to a hub in a manner that provides positive support to each blade at forward and rearward regions thereof, for improved stability;        to provide, in a centrifugal fan impeller, impeller blades and blade-supporting struts with profiles shaped for improved aerodynamic efficiency; and        to provide an impeller construction that facilitates independent optimization of blade inlet and discharge angles.        